docs: def dump_p(self, filename):
          """ Dump parameter values (``fit.p``) into file ``filename``.
  
          ``fit.dump_p(filename)`` saves the best-fit parameter values
          (``fit.p``) from a ``nonlinear_fit`` called ``fit``. These values
          are recovered using
          ``p = nonlinear_fit.load_parameters(filename)``
          where ``p``'s layout is the same as that of ``fit.p``.
          """
          warnings.warn(
              "nonlinear_fit.dump_p deprecated; use gvar.dump instead",
              DeprecationWarning
              )
          with open(filename, "wb") as f:
              pickle.dump(self.palt, f)